1. Field
This invention relates to compound archery bows. It is particularly directed to an improved bearing assembly for the pulley assemblies of such bows.
2. State of the Art
Compound archery bows commonly carry assemblies of pulley members (usually called “eccentrics” or “cams”) eccentrically mounted on axles in association with respective bow limbs. These limbs extend in opposite directions from a grip (usually comprising a central portion of a handle riser). The rigging for compound bows includes a bowstring trained around the pulley members of the system, the string being received by grooves or other functionally equivalent features at the perimeters of the pulleys. The eccentric pulley assemblies are conventionally mounted to rotate (pivot) on an axle within a notch at the distal end of the limb, or within a bracket structure carried by the limb tip. The eccentrics include one or more pivot holes substantially offset from center, whereby to provide for a reduction in the holding force felt at the nocking point of the bowstring, as the string is moved to its fully drawn condition.
Compound bows and various exemplary riggings, including pulley assemblies, are described by U.S. Pat. Nos. 3,486,495; 3,990,425; 4,748,962; 4,774,927; 4,967,721; 6,763,818 and 7,441,555, the disclosures of which are incorporated as a portion of this disclosure.
The rigging for compound bows typically includes cable segments, which may be end stretches extending from an integral bowstring. More often, however, the cable segments are separate elements, each connecting at one end, directly or indirectly, e.g., through structure associated with the pulley assembly, to a terminal end of the bowstring. The remaining (distal) ends of the cable segments are conventionally connected to the opposite bow limb or structure, such as the pivot axle mount of the pulley assembly carried by that limb. In any case, each cable segment includes one or two stretches oriented approximately parallel the bowstring.
“Approximately parallel,” is intentionally fluid in context, merely recognizing that the cable segments and bowstring all extend generally across, but out of contact with, the handle riser portion of the bow between the pulley assemblies, or other structure, carried by the respective bow limbs. All of the cable stretches are thus confined within a space defined by reference planes straddling the handle riser and containing the bowstring. The cable stretches are commonly positioned to one side of the bowstring to avoid interference with the nocking point of the bowstring. It is common practice to mount cable guard rods or other structures to the handle riser. These structures are positioned physically to hold the cables away from the plane of travel of the bowstring. Compound bows have sometimes been configured to position cables on opposite sides of a bowstring so that an arrow may be cast in the plane of the bowstring between cable stretches.
With a compound bow oriented in its normal position of use, it is conventional to consider the bow as being oriented vertically. Unless otherwise stated, the bows referred to in this disclosure are assumed to be in this “vertical” orientation. The handle riser is thus considered to have an “upper end,” a “lower end” and a central grip portion. The limb extending from the upper end of the handle riser may be referred to as “a first limb” or the “upper limb,” in either case terminating in an “upper limb tip.” Corresponding terminology is applied to the “second limb,” which extends from the lower end of the handle riser. The bowstring is assumed to travel in a plane (“operating plane”) of travel between a fully drawn condition and braced or at rest condition. Cable stretches may be viewed as being positioned to the left or right of the plane of travel of the bowstring, recognizing that in some rigging systems, a cable stretch may be to one side of that plane of travel along the first limb and to the opposite side of that plane of travel as the stretch proceeds to its point of attachment at the second limb.
U.S. Pat. Nos. 3,990,425; 6,990,970; 7,305,979 and 7,441,555 disclose rigging systems that cross-couple the pulley assemblies of a compound bow so that they are constrained to move in unison, thereby providing a self-tuning function to the bow. The term “cross-couple” (sometimes “cross-coupling,” or “cross-coupled”) designates a rigging in which a cable end that is conventionally attached to a pulley axel is instead attached to a synchronizing sheave of the pulley assembly.
The conventional practice in constructing compound bows has been to mount all pulley components onto stationary axles. Originally, the pulleys were provided with bushings, rotatably mounted on an axle. More recently, these bushings have been replaced with bearing assemblies of various kinds, Exemplary bearing arrangements for compound bows are described and illustrated by U.S. Pat. No. 6,415,780, the disclosure of which is also incorporated as a portion of this disclosure.
The pulley assemblies in common use currently are typically machined, or otherwise formed, from a common block of material. In some instances pulley components are connected together with pins, bolts or screws. In any case, all of the pulley members of the assembly form a unitary structure mounted to turn upon an axle. The axle may be clamped or otherwise fixed with respect to a limb tip of the bow. The '780 patent suggests that pulley assembly axles mounted to turn in bearing assemblies may be press fit into the pulley components. In practice, however, except for the pulley and axle assembly disclosed by parent application Ser. No. 12/074,930, operation of a compound bow is not negatively impacted by rotation of the axle with respect to either the limb tip or the pulley elements, provided the pulley assembly is free to turn around a transverse axis of rotation.
Historically, excessive limb breakage has been associated with the construction practice of positioning an axle directly through channels transverse and within a limb tip of a bow. This problem has been partially alleviated in some constructions by mounting the pulley assembly in a bracket fixed to a limb tip. The use of brackets for this purpose is thought to impact negatively upon bow performance because of the added bracket weight carried by the limb tip under dynamic conditions.
There remains a need for a mounting system capable of associating the limbs of compound archery devices and pulley assemblies of various constructions without the drawbacks and disadvantages of previous arrangements.